(a) Field of the Invention
The present invention relates to an automatic gain control device having a variable gain control interval, and a method thereof. More specifically, the present invention relates to an automatic gain control device for a wireless local area network (WLAN) system having a multiplexing antenna and a single antenna, and a method thereof.
(b) Description of the Related Art
In general, a signal is distorted in a digital realm when a gain of a received signal is out of a dynamic range of an analog to digital converter (A/D converter), and when the gain is set to be low, demodulation performance is deteriorated since a quantization noise is increased.
Some of commercial variable gain amplifiers operate in the digital realm to perform a scaling operation for a digital signal. Due to a variable gain amplifier (VGA) and a low noise amplifier (LNA), a commercial radio frequency (RF) chip may have wider dynamic range, and it controls a signal gain of a receiving terminal. A cellular system performs an automatic gain control based on an estimation result obtained by using a pilot while a link is formed between a transmitting terminal and a receiving terminal, and a quick, accurate, and stable gain controlling method is required in a packet-based wireless communication systems including a wireless local area network (LAN) since it is required to finish a gain controlling operation within a short preamble period.
In an automatic gain control method used in continuous mode communication, an initial convergent time is long, but gain controlling performance is very good and stable. In addition, the automatic gain controlling method used in the packet-based wireless communication uses a method for gradually reducing a difference between a measured receiving power value and a desired signal power value.
However, it is difficult to use the above methods in a high speed packet communication system since the initial convergent time thereof is long. As described, in the prior art, gain controlling operations of the VGA and LNA that are usually used in the commercial RF chip may not be efficiently performed since a device for controlling an LNA gain state is not considered when a gain is controlled. In addition, since complexity of the above methods is high, it is not efficient to use the methods in a multiple antenna system.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.